Abstract:

Systems and methods that facilitate the detection of a broken or damaged
screen in a laser PTV due to impact or shock through the measure or
monitoring of continuity or resistivity of a conductive trace applied to
the screen. In one embodiment, a screen damage detection system comprises
a clear conductive trace applied to the display screen preferably in a
serpentine configuration. Damage to the screen is detected when the hole
or crack in the screen is sufficiently large to open the conductive
trace. In another embodiment, a damage detection system comprises a clear
resistive film applied to the screen. The resistance is measured in the X
and Y axis to detect changes in the resistance of the coating due to a
crack or hole in the screen and disable the laser through a laser enable
output signal when a change in resistance greater than a predetermined
value is detected.

Claims:

1. A screen damage detection system for a laser PTV comprisinga conductive
trace disposed on the surface of a display screen of the PTV, anda damage
detection circuit coupled to the conductive trace and configured to
detect discontinuity in the conductive trace due to damage of the screen.

2. The system of claim 1 wherein the detected discontinuity is a function
of the resistivity of the trace.

3. The system of claim 1 wherein the trace is formed from a transparent
conductive material.

4. The system of claim 3 wherein the transparent conductive material is
indium tin oxide (ITO).

5. The system of claim 1 wherein the trace is formed in a serpentine
configuration.

6. The system of claim 1 wherein the pitch of the trace is less than one
half of the smallest size of a hole, crack or chip in the screen to be
detected.

7. The system of claim 1 wherein the circuit is adapted to cause the shut
down of a laser light source when discontinuity in the trace is detected.

8. The system of claim 7 wherein the circuit comprisesa comparator,a first
lead coupled to a first end of the trace and connected to electrical
ground,a second lead coupled to a second end of the trace and to a
negative input of the comparator,a pull-up resistor connected to the
second lead and a power source, andfirst and second divider resisters
connected to electrical ground and the power source and coupled in
parallel to a positive input of the comparator,wherein the comparator
being adapted to compare a reference voltage created by divider resistors
on the positive input of the comparator to the voltage on the negative
input of the comparator.

9. The system of claim 8 wherein the pull-up resister is adapted to pull
the negative input of the comparator high due to discontinuity in the
trace.

10. The system of claim 8 wherein the comparator is adapted to output an
output signal that corresponds to the high input on its negative input to
signal a control system to shut down a laser light source.

11. A screen damage detection system for a laser PTV comprisinga resistive
film disposed on a surface of a display screen of the PTV, anda damage
detection circuit coupled to the resistive film and configured to detect
damage to the screen as a function of a change in resistivity of the
film. 12. The system of claim 11 wherein the resistive film comprises a
thin metallic layer.

12. The system of claim 11 wherein the film is formed from a transparent
resistive material.

13. The system of claim 11 wherein the circuit detects a change in
resistivity as a function voltage drop across the film.

14. The system of claim 11 wherein the circuit is adapted to cause the
shut down of a laser light source when a change in resistivity is
detected.

15. The system of claim 14 wherein the circuit comprisesa first set of
electrodes positioned along the side edges of the screen,a second set of
electrodes positioned along the top and bottom edges of the screen,a
comparator circuit,a switch coupled to the comparator circuit,a current
source coupled to the comparator and the switch, andfirst and second sets
of wire leads coupled to the first and second set of electrodes and the
set of switches.

16. The system of claim 15 wherein the switch comprises a set of switches.

17. The system of claim 16 wherein the comparator circuit comprises an
analog-to-digital converter and a microprocessor, the microprocessor
records the normal resistance of screen in an undamaged state along the
axis extending between the electrodes of the first and second sets of
electrodes, controls the set of switches to sample the resistance along
each axis to detect changes in the resistance of the film and outputs a
disable signal when a change in resistance greater than a predetermined
value is detected.

18. The system of claim 17 wherein the comparator circuit comprise a
temperature sensor coupled to the microprocessor.

[0002]The embodiments described herein relate generally to televisions and
particularly to laser light source based televisions, and more
particularly, to systems and methods that facilitate the detection of a
broken or damage screen.

BACKGROUND INFORMATION

[0003]In laser projection televisions (PTVs), a laser light source is used
to illuminate images for projection on to the display screen. However, as
with other systems using laser light, there remains the potential risk to
the user or viewer of excessive exposure to the laser light should the
laser light become uncontained. In a laser PTV, containment failure can
occur due to a broken or damaged screen. The uncontained laser light
could hit the viewer directly in the eye or on the skin, which could
result in severe damage to the viewer's eye and/or skin.

[0004]Thus, systems and methods that facilitate the detection of a broken
or damaged screen are desirable.

SUMMARY

[0005]The embodiments provided herein are directed to systems and methods
that facilitate the detection of a broken or damaged screen in a laser
PTV due to impact or shock through the measure or monitoring of
continuity or resistivity of a conductive trace or coating applied to the
screen. In one embodiment, a screen damage detection system for a laser
PTV preferably comprises a clear, transparent or translucent conductive
trace formed of a clear, transparent or translucent conductive material
applied to the display screen preferably in a serpentine configuration.
The pitch of the trace is preferably less than half the size of a hole or
crack in the screen to be detected. Damage to the screen is detected when
the hole or crack in the screen is sufficiently large to open the
conductive trace. A laser enabled output signal is used to shut down the
laser source to prevent excessive laser light output.

[0006]In another embodiment, a damage detection system preferably
comprises a clear, transparent or translucent resistive coating or film,
such as a thin metallic layer, applied to the screen. The resistance is
preferably measured by applying a fixed current and measuring the voltage
drop across electrodes positioned along the edges of the screen. A
microprocessor, which records the normal resistance in the X and Y axis
of the undamaged screen, controls a set of switches to sample the X and Y
resistance to detect changes in the resistance of the coating due to a
crack or hole in the screen and disable or turn off the laser through a
laser enable output signal when a change in resistance greater than a
predetermined value is detected.

[0007]Other objects, systems, methods, features, and advantages of the
invention will be or will become apparent to one with skill in the art
upon examination of the following figures and detailed description. It is
intended that all such additional systems, methods, features and
advantages be included within this description, be within the scope of
this invention, and be protected by the accompanying claims. It will be
understood that the particular methods and apparatus are shown by way of
illustration only and not as limitations. As will be understood by those
skilled in the art, the principles and features explained herein may be
employed in various and numerous embodiments.

BRIEF DESCRIPTION OF THE FIGURES

[0008]The details of the example embodiments, including fabrication,
structure and operation, may be gleaned in part by study of the
accompanying figures, in which like reference numerals refer to like
parts. The components in the figures are not necessarily to scale,
emphasis instead being placed upon illustrating the principles of the
example embodiments. Moreover, all illustrations are intended to convey
concepts, where relative sizes, shapes and other detailed attributes may
be illustrated schematically rather than literally or precisely.

[0009]FIG. 1 is a side view schematic of a laser projection television
(PTV).

[0010]FIG. 2 is a schematic of a control system for the laser PTV shown in
FIG. 1 with an integrated screen damage detection system.

[0011]FIG. 3 is a plan view schematic of a screen damage detection system.

[0012]FIG. 4 is a plan view schematic of an alternate embodiment of a
screen damage detection system.

[0013]It should be noted that elements of similar structures or functions
are generally represented by like reference numerals for illustrative
purpose throughout the figures. It should also be noted that the figures
are only intended to facilitate the description of the preferred
embodiments.

DETAILED DESCRIPTION

[0014]Each of the additional features and teachings disclosed below can be
utilized separately or in conjunction with other features and teachings
to produce a screen damage detection circuit for a laser projection
television. Representative examples of the present invention, which
examples utilize many of these additional features and teachings both
separately and in combination, will now be described in further detail
with reference to the attached drawings. This detailed description is
merely intended to teach a person of skill in the art further details for
practicing preferred aspects of the present teachings and is not intended
to limit the scope of the invention. Therefore, combinations of features
and steps disclosed in the following detail description may not be
necessary to practice the invention in the broadest sense, and are
instead taught merely to particularly describe representative examples of
the present teachings.

[0015]Moreover, the various features of the representative examples and
the dependent claims may be combined in ways that are not specifically
and explicitly enumerated in order to provide additional useful
embodiments of the present teachings. In addition, it is expressly noted
that all features disclosed in the description and/or the claims are
intended to be disclosed separately and independently from each other for
the purpose of original disclosure, as well as for the purpose of
restricting the claimed subject matter independent of the compositions of
the features in the embodiments and/or the claims. It is also expressly
noted that all value ranges or indications of groups of entities disclose
every possible intermediate value or intermediate entity for the purpose
of original disclosure, as well as for the purpose of restricting the
claimed subject matter.

[0016]Turning in detail to the figures, FIG. 1 depicts a schematic of a
laser projection television (PTV) 10. The PTV 10 comprises a cabinet or
enclosure 12 housing an image projection engine or system 13, e.g., a
DLP, LCD or LCOS based projection engine or the like, projection optics
16 coupled to the image engine 13, a laser light 11 source coupled to the
image engine 13, a projection screen assembly 14 attached to the front of
the cabinet 12, and a mirror 18 optically coupled to the projection
screen assembly 14 and the image projection engine 13 and projection
optics 16. Also mounted in the interior 17 of the cabinet 12 is a control
module 32 comprising logic circuits and other electronic components.

[0017]Referring to FIG. 2, the PTV 10 preferably includes a control system
30 having a damage detection circuit 100 coupled to a conductive trace or
film 110 formed on the screen 14 and also coupled to the control module
32. The control module 32 is also coupled to the television's on screen
display (OSD) controller 42 and the laser light source 11. Both the OSD
controller 42 and the laser light source 11 are coupled to the
television's projection engine 13, which is operably coupled to the
screen 14.

[0018]The control module 32 preferably comprises a microprocessor 34,
non-volatile memory 36 and system software 38 stored in the memory 36.
The software 38 preferably includes a set of instructions used to control
the overall operation of the television 10 and, among other things, shut
down the operation of the laser light source 11 in response to a laser
enable signal received from the damage detection circuit 100.

[0019]The damage detection circuit 110 detects a damaged screen due to
impact or shock through the measure of continuity or resistivity of a
conductive trace or coating 112 applied to the screen 14. In one
embodiment, as depicted in FIG. 3, a damage detection system 100
comprises a clear, transparent or translucent conductive trace 112
preferably comprising indium tin oxide (ITO) or other clear, transparent
or translucent conductive material and applied to the screen 14
preferably in a serpentine configuration. The pitch of the trace 112 is
preferably less than half of the size of a hole or crack in the screen 14
to be detected. The damage detection circuit 110 includes a first lead
114 coupled to a first end of the trace 112 and connected to electrical
ground 116. A second lead 113 coupled to the other end of the trace 112
is connected to a pull-up resistor R3 to Vcc and a negative input of
a comparator 118. The comparator 118 compares a reference voltage, which
is created by divider resistors R1 an R2, on the positive input
of the comparator 118 to the voltage on the negative input of the
comparator 118. Damage to the screen 14 is detected when a hole or crack
in the screen 14 is sufficiently large to open the conductive trace 112.
With the trace 112 open, the pull-up resister R3 will pull the
negative input of the comparator 118 high and the output signal of the
comparator 118 will go low as a result. The output laser enable signal is
received and monitored by the control module 32, which will shut down the
laser light source 11, turn off the power to the laser light source or
disable a laser driver circuit to prevent excessive light output when a
low output laser enable signal is received.

[0020]In another embodiment, as depicted in FIG. 4, a damage detection
system 200 comprises a clear, transparent or translucent resistive
coating or film 212, such as a thin metallic layer, applied to the screen
14. The damage detection circuit 210 includes electrodes 213 and 215
positioned adjacent the edges of the screen 14. Wire leads 211, 214, 216
and 218 are attached to the electrodes 213 and 215 to enable a change in
resistance of the coating 212 to be measured in the X and Y axis to
detect a damaged screen 14. A set of switches 220 connect the X or Y
electrodes 213 and 215 to a comparator circuit 230 to measure the
resistance of the coating 212. The resistance is measured by applying a
fixed current through a suitable current source 222 and measuring the
voltage drop across the electrodes with an analog-to-digital converter
232 and a microprocessor 236. The microprocessor 236 controls the set of
switches 220 to sample the resistance in the X and Y axis and compares
the sampled resistance to a stored or recorded normal resistance in the X
and Y axis of the undamaged screen 14, to detect changes in the
resistance of the coating 212 due to a crack or hole in the screen 14.
The microprocessor 236 disables or shuts down the laser enable output
signal when a change in resistance greater than a predetermined value is
detected. The output laser enable signal is received and monitored by the
control module 32, which will shut down the laser light source 11 turn
off the power to the laser light source or disable a laser driver circuit
to prevent excessive light output when a change in resistance greater
than a predetermined value is detected.

[0021]A temperature sensor 234 can be connected to the microprocessor 236
to compensate for changes in the resistivity of the screen coating 212
due to ambient temperature changes.

[0022]In the foregoing specification, specific example embodiments have
been described. It will, however, be evident that various modifications
and changes may be made thereto without departing from the broader spirit
and scope of the invention. For example, the reader is to understand that
the specific ordering and combination of process actions shown in the
process flow diagrams described herein is merely illustrative, unless
otherwise stated, and the invention can be performed using different or
additional process actions, or a different combination or ordering of
process actions. As another example, each feature of one embodiment can
be mixed and matched with other features shown in other embodiments.
Features and processes known to those of ordinary skill may similarly be
incorporated as desired. Additionally and obviously, features may be
added or subtracted as desired. Accordingly, the invention is not to be
restricted except in light of the attached claims and their equivalents.